Today’s Question: Would you be able to explain when use of the quick mask is appropriate [in Photoshop] instead of a regular layer mask?
Tim’s Quick Answer: The Quick Mask feature in Photoshop is actually a tool for creating and modifying selections, while a layer mask is used to identify an area that an adjustment will apply to (or for creating a composite image). Since a selection can be used as the basis of a layer mask, you could use Quick Mask mode to create or modify your initial selection, then create a layer mask based on that selection, and fine-tune from there.
More Detail: Photoshop includes a variety of different tools for creating selections. Most of those tools involve either tracing along the edge of the object you want to select, or identifying the area to be selected based on sampling within the image.
The Quick Mask mode is an option for creating or modifying selections where you paint with white to indicate areas you want to select, and with black to indicate areas you don’t want selected. So, for example, you can use the Brush tool to identify (or modify) the area of a selection, or you could use the Lasso tool to trace along the edge of that selection. In other words, the Quick Mask mode is simply another tool available for creating and modifying selections.
A layer mask is used in conjunction with an adjustment layer (or an image layer) to apply a targeted adjustment (or to create a composite image). With a layer mask you can paint with white to identify areas you want to adjust (or have visible), and you can paint with black to identify areas you don’t want to adjust (or that you want to hide).
So, Quick Mask mode and layer masks are very similar, in that you’re able to paint with white and black to identify areas of the image. The only difference is the context. You can use Quick Mask mode if you prefer painting to define a selection, and then create a layer mask based on the selection. And regardless of how you created a selection (or whether you created a selection at all) you can also paint with white and black on a layer mask to refine that mask that is being used as a “stencil” for the image.